In recent years, detection targets, which appear in video pictures imaged by monitoring cameras and so forth installed in various places such as offices, shopping centers, and shopping areas, have been detected.
As a technology for detecting humans as detection targets, a technology for detecting humans from an image by applying detectors for detecting a part of a physical body of a human or a whole body thereof is disclosed in, for example, Japanese Laid-open Patent Publication No. 2013-45433.